OP Truths & Myths

Let’s start with appreciation for Penny Simkin’s brave confrontation of a dogmatic trend that has arisen over the years. Penny Simkin has a wonderful literature review presentation she calls, “The OP Fetus: How little we know.” Parents and professionals alike have some misunderstandings about the influence of posterior presentation on labor. We might hear surprise at finding an OP baby even in a long labor.

“She didn’t have back labor, so I didn’t think the baby was posterior.”

“We did everything we could… we tried hands-and-knees position.”

Sometimes a midwife or doctor will say they don’t pay much attention to a head-down baby’s position in late pregnancy because some posterior babies come out vaginally.

Spinning Babies is concerned about the 15-30% of OP babies that need more help than strong labor and the hands-and-knees position.

A 2005 study by Ellice Lieberman and her research group in Boston busted some of the myths about posterior labors. Unfortunately, people reading the study could also conclude that fetal position changes at random throughout the course of labor. Yet, in reading the data carefully, we find several consistencies with previous research on the posterior fetal presentation and its effects on labor.

There is a difference in ROT/LOT starting positions brought to light by Jean Sutton in her Understanding and Teaching Optimal Foetal Positioning book. I’ve been able to observe the differences in labors when babies enter the pelvis from mother’s right compared to the left.

The back of baby’s head is to the mother’s left or right (Occiput Transverse position) in about half (48.9%) of babies. Jean Sutton re-introduced attention to the shape of the human uterus. It is higher on the right than the left, making the right wall steeper and the left wall rounder. Babies, therefore, may be curled in a way that makes birth easier if they come down from the left (head down babies, that is). So the conclusion that fetal rotation is random may be somewhat premature.

First babies may have more challenges with an occiput posterior or right occiput transverse position than subsequent babies, but that, too, isn’t always true.

There may be truth and may be myth in what we believe about fetal positioning. So, I’d like to start with the myths of the OP position which Penny Simkin has helped us identify and then give my two cents worth– and some of that I ask you to take on credit! I’ll talk about bony and soft tissue contributors to whether or not a posterior baby may get stuck or delayed.

The Myths

MYTH: It is important to know the fetal position.

Penny Simkin lists this myth in her talk about What We Don’t Know About the OP Baby. Midwives have been debating the importance of fetal position — gently — for years. And I agree this is a myth.

Gail’s thought: Finding a solution for a non-progressing labor can occur without knowing the fetal position.

The muscles, ligaments and pelvic diameters may need accommodation in a slow, or a painful, labor regardless of fetal position. In other words, tension in the psoas pair of muscles or pelvic floor can delay an anterior baby and a posterior baby. Extension of the anterior baby’s head can prevent engagement in some pelvises. The main point is that we can, when needed, promote progress regardless of fetal position.

MYTH: If we prevent OP before labor than we can prevent OP in labor

To answer this question correctly we would have to study 2nd trimester prevention exercises among one group of women with no prevention methods in another group. Why? Because while most babies that start labor in an OP position will rotate to OA before the end of labor, there is a consistent small group of babies who are OP throughout labor.

These need Spinning Babies. But how do we identify this group? Why not help the other mothers, too?

The point I’m making is, that just because most OP babies rotate to OA (about 87%, according to Gardberg), we shouldn’t ignore the 15% (Lieberman) who are OP when they are born, either vaginally or via cesarean.

MYTH: If the baby is Occiput Anterior (OA, the “best” starting position) in early labor the baby will stay in a good position throughout labor.

The recent Lieberman study confirmed statistical trends of earlier studies. 83% of the OA babies who were OA in early labor were OA when they came out. But a small 5.4% rotated to a direct Occiput Posterior position for birth.

MYTH: Midwives and Doctors can tell the baby’s position.

While this is sometimes truth, in reality sometimes we can and sometimes we can’t. There are three common ways a baby’s position is sought:

By hands-on palpation, or feeling the abdomen. The bumps in the belly mean something to a practiced hand. The problem is in the variation of bellies and bumps. Sometimes they don’t make a picture that the person feeling can make out. Bellys come in different thicknesses. Babies sometimes are curled up in interesting ways. Lots of amniotic fluid or muscle strength can hide details that might be needed to “see” the position.

Feeling inside, through the open cervix, sometimes gives clues. But the little sutures (not stitches, but lines showing where the skull bones meet) can be just out of reach or the edge of the soft spot (fontanel) can feel like a suture, oddly enough. Feeling babies position is not as simple as it looks in the books or on the plastic chart some hospital labor and delivery units have.

Ultrasound can tell the baby’s position. Funny we rely so wholeheartedly on technology. We are looking through dark water to see a 3-D person displayed on a 2-D computer screen. There can be blurred pictures of the crucial landmarks of the baby’s head or the viewer can make a mistake.

Dr. Karen Davidson, the ultrasound sonologist for the Lieberman group studying 1,766 women in labor (see a discussion on this interesting study by clicking on a link below), found she had to exclude 162 women because their ultrasound pictures were uninterpretable. In the first six-months of the study she found 13% of early labor ultrasounds were uninterpretable. She got really good at it as the study went on, but she was their expert to begin with, so I would think her early rates must be at least on par with the nation’s ultrasound interpreters.

Of the 1,562 births remaining in the Lieberman study, 51% had an interpretable ultrasound picture in late labor. That means 49% didn’t. I don’t think we can hang our hats on ultrasound. And furthermore, how the baby’s back is situated doesn’t always tell us how the head is facing.

MYTH: Back pain is a sign of an Occiput Posterior (OP) baby.

Some women in of each of these categories are likely to get some back pain in labor:

Short women

Women who aren’t flexible

Women who’ve had accidents

Women who have weak back muscles

Some of the women with posterior babies or babies who have one of their arms up in late labor

The women with OP babies in early labor (3 to 4 cm mostly) enrolling in the Lieberman study did not report more back pain at 3-4 cm dilation. As a doula of women with and without epidural pain relief, many without, I have noted that OP back pain, when it does come, often comes between 4 and 6 cm.

Some women have relatively straightforward OP labors, if we are still permitted to call labors by the fetal position name. These women often do not report back pain at an intensity to get attention. Some have no more labor pain in their backs than they do in the front. A few women have severe back pain early in labor, at 2 cm. These women are candidates for an inversion as soon as possible, if they are up for it. Back pain is more about the fit of the baby than the position. Some posterior babies fit their mother’s pelvises better than others.

MYTH: When a woman is having prolonged labor without back pain, it is from a reason other than posterior position.

Oh, thank you, Penny, for bringing this myth to our attention. I can’t list the times a midwife, doula or nurse has told me their frustration at not being able to think of a labor progress trick to help a woman in long labor. They often say something quite close to this, “I thought of the Open-Knee Chest position (or another technique) but didn’t try it because she didn’t have back pain. While the cesarean was being done, the doctor said the baby was posterior and that’s why the baby wasn’t coming through the pelvis.”

A delay or a stall in labor, with or without back pain can often be corrected by one form of inversion or another. Check out Labor Progress and more technique information here.

Back pain, with or without a stall in labor, may also be soothed by inversion.

Sometimes back pain is from a spasm in a ligament low in the back of the uterus, such as the ligament holding the cervix to the sacrum. Inversion gives that ligament a gentle stretch and then when the mom gets up the ligament can relax. Ahhh.

There are some protective guidelines about inversion. See the article and ask your care provider: “Is there a medical reason not to do it?” This great little question also comes to us via Penny Simkin.

MYTH: Position changes can change the OP position in labor

This hasn’t been studied like I’d like to it to be studied. The studies aren’t designed in a way that will answer anything, but regardless, 30 minutes of position changes are not enough to overcome the tension in the womb holding the baby in an unfavorable position.

These studies are why I developed the “3 Principles of Spinning Babies.” First, you have to relax the involuntary muscles, including the muscle fibers mingled in the uterine ligaments. Second, you get gravity helping and third, move the pelvis in ways that open the level of the pelvis that the baby’s head is resting at.

If the head is stuck at the brim, you don’t open the bottom of the pelvis, for instance, and wonder why squatting works for some women and not for others. If your front doorbell rings, do you open the back door and wonder where you company is at?

Pelvic shape and size does have an effect on the course of a posterior labor in a small percentage of women. A pelvic shape which is longer front to back allows a few women to have a posterior baby without back labor, as long as there isn’t another reason for backache, like a muscle spasm.

A pelvic shape which is triangular called an android pelvis, can make it hard for a larger, posterior baby to fit through. A woman with a smaller than average android pelvis will need to, in my observations, eat carefully to get good protein and vegetables without a lot of sweets and white bread. She will have to work on her babies position in the 2nd trimester, especially if she is a first-time mom. That way she can avoid the scenario I have often seen of being 8 months pregnant and trying to get a large OP baby to turn around and get settled in the brim facing the back right SI joint.

The baby’s back shifts right and left and right again, trying to turn his little forehead out of the narrow pointy space at the mother’s pubic bone. But the pelvis isn’t round so he can’t. He’ll have to come up and out, away from the brim to turn. He can only do that if the mom relaxes her ligaments, and gets upside down a bit each day.

It isn’t always comfortable, of course, to be 8 months pregnant and hang upside down for a minute. And even then, some of these moms need body work to overcome the muscle spasms in their round or broad ligaments. It’s much easier to do at 4 and 5 months pregnant. Even 6 months. If these few OP babies aren’t able to navigate their mother’s pelvic brim, they will have to be born by cesarean. The problem is that few people, and I mean providers, can tell who will be the one that gets stuck and who will be the one to get through.

A woman with a round, gynecoid pelvis has a much better chance of having her posterior baby rotate in labor. Depending on various factors, like eating in labor, keeping hydrated, leaning forward, being patient, resting belly down (somewhat), avoiding positions on her back, having her water broke or an epidural that increases the likelihood of a challenge with the labor (length, vacuum or surgery), her baby may come around readily or only eventually. A long labor can soften up tight spots on the route out.

Pelvic shape isn’t the only consideration, of course. The soft tissues are more often the case, especially when they aren’t soft at all!

References

The OP fetus: How little we know, Penny Simkin

Changes in Fetal Position During Labor and their Association with Epidural Analgesia, Ellice Lieberman et al.

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